1. Field of the Invention
The present invention is directed to automotive vehicle transmissions and more particular to pressure regulating valves for controlling oil flow through hydraulic circuits from an oil pump to both a torque converter and a lubrication/relief valve and to a pressure regulator balance port and to a method of modifying valve lands to provide for increased fluid supply to the torque converter and to establish a steady stream progressive flow rate of oil into the hydraulic circuits to improve torque converter clutch apply and release functions and to reduce heat buildup in the transmission to prevent torque converter damage or burn out.
2. Brief Description of the Prior Art
The majority of automatic transmission pressure regulation systems presently in use operate on a pulsed delivery principle. This pulsed delivery is the result of the valve's mechanical properties. Conventional valves are produced on automatic lathes and are round when viewed from an end view. Such valves have a plurality of outwardly extending lands which function to block or establish oil flow to or from lube circuits and components of the transmission such as the torque converter and lubrication and relief valve circuits. Conventional lands when viewed from the side appear to have squared 90° corners in that the front, rear and outer faces thereof and thus are planar along any given line. Although forming the lands with flat faces is easy and economical, in operation, the valves must cycle IN and OUT, opening and closing their respective flow ports to regulate oil flow thus creating a hydraulic pulse during each cycle. In essence, there is an instant charge or pulse of oil being sent to the torque convert and the lubrication relief valve circuits as the lands move to open flow to the inlet ports thereto.
In addition, automatic transmissions do not have perfectly sealed hydraulic circuits, and some leakage occurs, such in clutch drum apply circuits, accumulators, servos, at valves and plugs in the valve body, or loss of output efficiency in the transmission pump assembly due to internal “backwash”. Further, leakage increases as oil is heated and becomes less viscous.
By way of example, if, as in the Honda 4 & 5 speed automatic, a transmission pump is not designed with sufficient output capacity, system wide pressure will fall below the minimum requirements and begin to shut down secondary systems, like torque converter fill and flow to the transmission cooler.
The pressure regular valve springs in the Honda 4 and 5 speed transmissions are calibrated to regulate system pressure to a minimum of approximately 118 psi, and a maximum of approximately 210 psi, depending on operating conditions. Although the pressure regulator may be able to sustain the pressure within the circuits while the fluid is cooler and thicker, under hotter operating conditions, and when the vehicle is at a stop and transmission is in a drive gear at idle, the pump will not be able to produce enough gallons per minute (GPM) to overcome all the accumulated leaks and maintain pressure sufficient to hold the pressure regulator valve open against valve springs. Main line pressure then drops well below the minimum desired 118 psi. It is typical to see HOT pressure readings of 90 psi at idle, and VERY HOT readings as low as 60 psi. But any time the pressure falls below 118 psi, the pressure regulator valve closes, shutting off fluid flow to converter, cooler, and lubrication circuits. At this point the pressure regulator valve is not functioning and there is insufficient fluid being supplied to the torque converter. When at a stop, if there is not sufficient flow to hold the converter clutch released, it will drag and burn out the clutch lining (a layer of friction material bonded to the damper assembly). If the pressure regulator closes while the control system has the converter clutch in APPLY mode, there will be insufficient pressure to keep it firmly applied, and slippage occurs. This slippage also results in clutch lining burnout.
In view of the foregoing, there is a need to improve the operating characteristics of the pressure regulator control valve used on some conventional automotive transmissions in order to avoid the problems associated with pulsed oil supply and insufficient volume flow to the torque converter and lube circuits, and to improve supply of oil from the transmission pump to the torque converter to prevent overheating and damage.